1. Field
The following description relates to a fuel cell and a method of manufacturing the same, in which an effective brazing process can be performed between a unit cell and a cell fixing member such as a cell cap or cell connector.
2. Description of the Related Art
A fuel cell is a cell that converts chemical energy generated by oxidation into electric energy. The fuel cell is an eco-friendly technology that generates electric energy from materials such as oxygen and hydrogen, which are abundant on the Earth. In the fuel cell, an electrochemical reaction is performed as an inverse reaction of the electrolysis of water by respectively supplying oxygen and fuel gas to a cathode and an anode, thereby producing electricity, heat and water. Therefore, the fuel cell produces electricity at high efficiency without causing pollution. In the fuel cell, the discharged material in the electricity generating process is mostly only water. Hence, the concern about pollution is very low, and generation efficiency is improved by about 40% or higher as compared with existing generation technologies. Also, unlike general heat engines, since a mechanically moving part is not required unlike general heat engines, the fuel cell has the advantages of miniaturization, low noise, and the like.
Fuel cells can be classified into an alkaline fuel cell (AFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a polymer electrolyte membrane fuel cell (PEMFC) or a solid oxide fuel cell (SOFC) according to the kind of utilized electrolyte.
Among these fuel cells, the SOFC is widely used because the position of an electrolyte is easily controlled, there is no concern about the exhaustion of fuel, and the lifetime of a material is long. The SOFC can be divided into a tube type or a plate type according to the shape of its unit cell. The tube type has been used and studied in anode-supported fuel cells.
Generally, in a cylindrical SOFC, the inside and outside of the cell have electrodes that differ from each other, and therefore, different kinds of fuels are supplied to the electrodes, respectively. In this case, when cracks are generated at a sealing portion due to the weakness of the sealing between a cell and a cell fixing member, both of the fuels are mixed and ignited at a high temperature. As a result, the temperature of the cell is rapidly increased, and hence, the degradation of the cell is caused. Therefore, a sealing process is very important.